Protocols/MSNP/MSN Protocol Version 13
MSNP13 is the protocol version introduced with Windows Live Messenger 8.0. It is based on MSNP12 but incompatible due to changes in how the client processes the contact list.
Now that Windows Live Messenger 8 final is live, MSNP13 is working with the usual server, messenger.hotmail.com on port 1863. Note: If you have signed up for the Yahoo! Interoperability BETA, you need to support MSNP14!
MSNP13 also introduces full compatibility with Offline Messaging (previous clients could only receive OIMs), which is documented here.